The present invention relates to a dendritic cell activation factor, to methods of enhancing a lymphocyte-mediated immune response in vivo, and to dendritic cell populations useful in the manipulation of cellular and humoral immune responses.
Vaccination is an efficient means of preventing death or disability from infectious diseases. The success of this method in the field of infectious disease has also stimulated interest in utilizing vaccination in the treatment or prevention of neoplastic disease. Despite the successes achieved with the use of vaccines, however, there are still many challenges in the field of vaccine development. Parenteral routes of administration, the numbers of different vaccinations required and the need for, and frequency of, booster immunizations all impede efforts to control or eliminate disease.
One such difficulty is lack of immunogenicity in an antigen, i.e., the antigen is unable to promote an effective immune response against the pathogen. In addition, certain antigens may elicit only a certain type of immune response, for example, a cell-mediated or a humoral response. Adjuvants are substances that enhance, augment or potentiate an immune response, and can in some instances be used to promote one type of immune response over another. Although numerous vaccine adjuvants are known, alum is the only adjuvant widely used in humans.
Dendritic cells are a heterogeneous cell population with distinctive morphology and a widespread tissue distribution (Steinman, R. M., Annu. Rev. Immunol., 9:271-296, 1991). Dendritic cells are referred to as xe2x80x9cprofessionalxe2x80x9d antigen presenting cells, and have a high capacity for sensitizing MHC-restricted T cells. Thus, there is growing interest in using dendritic cells ex vivo as tumor or infectious disease vaccine adjuvants (see, for example, Romani, et al., J. Exp. Med., 180:83, 1994). Therefore, an agent that enhanced the ability of dendritic cells to stimulate an immune response would be of wide importance.
The present invention pertains to a method of activating dendritic cells to enhance antigen presenting capacity. The activated, antigen-presenting dendritic cells of the invention are useful as vaccine adjuvants.
The invention also provides a method of generating large quantities of antigen-presenting dendritic cells ex vivo. Following collection of an individual""s CD34+ hematopoietic progenitors and stem cells, cytokines such as granulocyte-macrophage colony stimulating factor (GM-CSF) and flt-3 ligand (flt3-L) can be used to expand the cells in vitro and to drive them to differentiate into cells of the dendritic cell lineage. Cytokines can also be used to increase the numbers of CD34+ cells in circulation prior to collection. The resulting dendritic cells are exposed to an antigen one wishes to elicit an immune response against, and allowed to process the antigen (this procedure is sometimes referred to in the art as xe2x80x9cantigen-pulsingxe2x80x9d). The antigen-pulsed (or antigen-expressing) dendritic cells are then activated with a CD40 binding protein, and subsequently administered to the individual.
An alternate method for preparing dendritic cells that present antigen is to transfect the dendritic cells with a gene encoding an antigen or a specific polypeptide derived therefrom. Once the dendritic cells express the antigen in the context of MHC, the dendritic cells are activated with a CD40 binding protein, and subsequently administered to the individual to provide a stronger and improved immune response to the antigen.
The activated antigen-presenting dendritic cells can also be used as a vaccine adjuvant and can be administered prior to, concurrently with or subsequent to antigen administration. Moreover, the dendritic cells can be administered to the individual prior to, concurrently with or subsequent to administration of cytokines that modulate an immune response, for example a CD40 binding protein (i.e., soluble CD40L), or a soluble CD83 molecule. Additional useful cytokines include, but are not limited to, Interleukins (IL) 1, 2, 4, 5, 6, 7, 10, 12 and 15, colony stimulating factors (CSF) such as GM-CSF, granulocyte colony stimulating factor (G-CSF), or GM-CSF/IL-3 fusion proteins, or other cytokines such as TNF-xcex1 or c-kit ligand. Moreover, biologically active derivatives of these cytokines; and combinations thereof will also be useful.
The invention also provides for the ex vivo preparation of antigen-specific T cells. Following the procedures described above for preparing large numbers of antigen-presenting dendritic cells ex vivo, the collected antigen-presenting dendritic cells are used to generate antigen-specific T cells from naive T cells that have been collected from the individual. After the antigen has been adequately presented to the T cells generated, the antigen-specific T cells can be administered to the individual.